Ribosome and RNA Structure and Function: At the present time, more needs to be learned about ribosome structure such as particle surface structure, amount and nature of RNA exposed, and RNA functions to fully understand the mechanism and regulation of protein synthesis. The aim of the proposed work is to gain information on the structure and function of Escherichia coli ribosomes, in particular, the nature of the exposed RNA on the surface of the ribosomes and exposed proteins to fully understand the mechanism and regulation of protein synthesis. One approach to ribosome structure that this laboratory is currently using is the modification of the intact particles, either with enzymes or by chemical means and the identification of the altered components. Information is being sought with respect to a) the nature of the exposed 5S RNA on the surface of ribosomes and the role of the 5S RNA in protein synthesis; b) the exposed proteins in the 70S ribosome; and c) the mechanism of interaction of aminoglycoside antibiotics with the ribosomes. In addition, the functional capacity in protein synthesis of ribosomes having modified RNA regions is being studied. This should yield information on the functional capacity (or lack) of the specific RNA regions in various aspects of protein synthesis.